Both options are not very useful in my opinion. The first one opens the Disk Usage analyzer without much info about the problem.

The message appear after connecting remote android device to my computer. Initially I thought that problem is related to the new added device. But after some investigation I found out that problem is related to the Linux Mint boot folder.

The original information from the examine button is not very useful. Instead of this you can use this command to find what is the current space under /boot: